1. Field of the Invention
The present invention relates to brakes and, more particularly, to spring-actuated, hydraulically releasable brakes, including single spring stack sliding caliper brakes and dual spring stack fixed caliper brakes.
2. Description of the Related Art
Spring-actuated, hydraulically releasable brakes are known which employ actuating springs to urge brake pads against brake discs and hydraulic piston and cylinder assemblies for releasing the brake pads from fictional engagement with the brake discs against the action of the springs.
After repeated use, the brake pads become worn and consequently the effectiveness of the brakes is reduced. However, due to the high braking capacities, direct acting functions and small retracted lining clearances of spring-actuated, hydraulically releasable brakes, automatic wear adjusters have not been common in such brakes. Not only does lack of adjustment of the brakes result in reduced braking capacities, but it can also severely reduce the fatigue life of the actuating springs. It has therefore usually been necessary to counteract brake pad or lining wear by manual adjustment of the brakes. However, manual brake adjustment is time-consuming and risky.
It is, accordingly, an object of the present invention to provide a novel and improved spring-actuated, hydraulically releasable brake which is maintained in proper adjustment, regardless of lining wear and without manual adjustment of the brake.
According to the present invention, there is provided a spring-activated, hydraulically releasable brake having first and second brake pads, located at opposite sides of a brake disc, with springs urging the first brake pad against the brake disc, a hydraulic piston and cylinder assembly operable to displace the first pad from the brake disc against the action of the springs, and an automatic brake adjustment mechanism responsive to the amount of the displacement of the first brake pad from the brake disc by the hydraulic piston and cylinder assembly for adjusting the first brake pad toward the brake disc when such displacement exceeds a determined amount.
In a preferred embodiment of the invention, the automatic brake adjustment mechanism includes a pivotable member in the path of movement of the piston of the hydraulic piston and cylinder assembly, and a link extending between the pivotable member and a one-way clutch. A lost motion connection is provided between the linkage and the one-way clutch, so that the latter is operated to rotate a shaft extending from the one-way clutch to the piston rod of the piston only when the predetermined amount of the displacement is exceeded. A threaded connection is provided between the shaft and the piston rod, so that rotation of the piston rod shaft causes longitudinal adjustment movement of the piston rod and, therewith, of the first brake pad toward the brake disc.